Mobile communication equipment (a mobile terminal) such as a mobile phone is configured to cope with a plurality of communication systems. That is, in a transmission/reception unit (a front end) of the mobile phone, a plurality of circuit systems is incorporated to perform the transmission/reception of a plurality of communication systems. For example, as a method which enables a call between mobile phones (for example, cellular phones) which differ in the communication method (system), a dual band communication method has been known. With respect to the dual band method, there have been known a dual band method which adopts a GSM (Global System for Mobile Communication) using a carrier frequency band of 880 to 915 MHz and a DCS-1800 (Digital Cellular System 1800) using a carrier frequency band of 1710 to 1785 MHz and a high frequency power amplifier for dual bands.
Further, in Japanese Unexamined Patent Publication No. Hei 11 (1999)-186921 (laid open to public inspection on Jul. 9, 1999), a multiple band mobile body communication device which is applicable to mobile phone systems such as a PCN (Personal Communication Network: DCS-1800), PCS (Personal Communications Service: DCS-1900), GSM and the like is disclosed.
Further, at a front end of the mobile phone, a high frequency part analogue signal processing circuit for GSM is formed into a module. For example, there has been known a RF (Radio Frequency) power module for GSM of a dual band or a triple band using a MOSFET (Metal Oxide Semiconductor Field-Effect-Transistor).
The dual band method processes signals of two communication systems such as the GSM method and the DCS 1800 method, while the triple band method processes signals of three communication systems such as the dual band method, the DCS (Digital Cellular System) 1800 and the PCS 1900 method. As the GSM, a GSM900 or a GSM 850 is incorporated.
Further, in the high frequency power module, one-chip semiconductor element which is formed by integrating an LNA, a mixer, a PLL (Phase-Locked Loop) synthesizer, auto-calibration-added PGA (Programmable Gain Amplifier), an IQ modulator/demodulator, an offset PLL, a VCO (Voltage-Controlled Oscillator) and the like in a monolithic manner is incorporated.
Further, in Japanese Unexamined Patent Publication No. 2002-76235 discloses a dual band transmission/reception semiconductor integrated circuit. A differential low noise amplifier (comprised of two unit amplifiers in which signals having phases inverted from each other are inputted) which is incorporated into the dual band transmission/reception semiconductor integrated circuit includes a pair of input terminals and a pair of output terminals, wherein ground pins of the amplifier formed of a pair of differential amplifiers are arranged close to each other. Further, input pins and the ground pins of the same amplifier are arranged close to each other. Accordingly, this patent literature discloses a technique to enhance the gain of the differential amplifier in which by making the signals of neighboring pins have phases inverse from each other and by making use of the transformer junction between pins, the impedance applied to the transistor emitter can be reduced.
On the other hand, there has been a demand for the miniaturization and the reduction of weight with respect to the mobile phone for facilitating the carrying of the mobile phone. As a result, there has been a demand for the miniaturization and the reduction of weight also with respect to electronic parts such as the high frequency power module or the like.
There exist various semiconductor devices depending on the packaging modes and, as one of these semiconductor devices, there has been known a non-lead type semiconductor device which exposes leads (external electrode terminals) on a back surface (mounting surface) of a sealing body (package) made of insulation resin and prevents the projection of long leads from side surface of the sealing body.
As the non-lead type semiconductor device, a SON (Small Outline Non-Leaded Package) which exposes leads along two opposing sides on a back surface of the sealing body and a QFN (Quad Flat Non-leaded Package) which exposes leads on four sides on a back surface of the sealing body can be named. The non-lead type semiconductor device which is miniaturized and is free from bending of leads is described in Japanese Unexamined Patent Publication No. 2001-313363, for example.
The resin-sealed type semiconductor device described in this literature has the following structure. That is, the semiconductor device includes an island having a die pad to which a semiconductor chip is fixed and a wire bonding portion to which wires are connected, wherein the semiconductor chip is fixed to the die pad and respective electrode terminals of the semiconductor chip are connected with the leads and the wire bonding portion of the island. A gap is defined between the die pad and the wire bonding portion so as to prevent the separation or the cutting of the bonded wire due to a thermal stress. In such the structure, by connecting an earth terminal of the semiconductor chip and the island using a wire, the semiconductor chip can be connected with a printed circuit board or the like using the island as a ground lead.
Further, in Japanese Unexamined Patent Publication No. Hei 11 (1999)-251494, there is a description with respect to a high frequency device in which the lead structure which is used in a mobile phone or the like and grounds a semiconductor element mounting portion adopts a gull wing type. In the technique, while electrodes of the semiconductor element are connected with leads using wires, a die pad is made use of as a grounding electrode and hence, the electrodes of the semiconductor element and a semiconductor mounting portion are connected with each other using wires (down-bonding). To perform the down-bonding, the semiconductor element mounting portion is configured such that the semiconductor element mounting portion is made larger than the semiconductor element and, in a mounted state, a peripheral portion of the semiconductor element mounting portion projects to the outside of the semiconductor element, and the wires are connected to these portions.
The applicant of the present invention has studied the adoption of a technique in which a high frequency power module is incorporated into the non-lead type semiconductor device and, for stabilizing the ground potential, ground terminals of respective circuit parts which comprise the high frequency power module are electrically connected with tabs by wires. By adopting the down-bonding, the number of external electrode terminals can be decreased and hence, the package can be minimized whereby the semiconductor device can be eventually miniaturized.
However, it has been found that the following drawbacks arise with respect to the high frequency power module which is used for the radio communication system (communication system).
In the reception system of the mobile phone, although signals which are caught with an antenna are amplified by a low noise amplifier (LNA), the input signals are extremely weak. Accordingly, the potential of the tab which is the common terminal, that is, the ground potential is fluctuated or changed in response to the operation of the respective circuit parts, particularly the operation of an oscillator which is periodically operated. Due to such fluctuation of the ground potential, a crosstalk is generated between some circuit parts and hence, the output is fluctuated whereby it is impossible to conduct a favorable call.
Particularly, the distortion of signal waveforms attributed to an induced current caused by the crosstalk between leads or the fluctuation of the ground potential is outputted from the communication system and the output signals enter the communication system in use thus generating noises.
As the circuit parts which are liable to easily receive the influence of the fluctuation of the ground potential and the crosstalk, an RFVCO (high frequency voltage control oscillator) and the like can be named besides the low noise amplifier (LNA).
In view of the above, inventors of the present invention come up with an idea that with respect to the low noise amplifier or RFVCO, instead of connecting the ground terminals among the electrode terminals of the semiconductor element with the tab which serves as the common terminal using the wires, the ground terminals are connected with an independent lead terminal (external electrode terminal) using wires so that the influence of the fluctuation of the ground potential when other circuit parts are turned on or off can be reduced. Then, the inventions have arrived at the present invention.
Accordingly, it is an object of the present invention to provide a semiconductor device provided with the down-bonding structure, wherein among circuits which are formed in the semiconductor element, the ground potentials in the specified circuit parts are configured to hardly receive the influence of the ground potential of remaining circuit parts.
It is another object of the present invention to provide a high frequency power module in which a circuit part such as a low noise amplifier, an RFVCO or the like hardly receives the influence of a crosstalk generated due to the fluctuation of the ground potential in other circuit part.
It is still another object of the present invention to provide a radio communication device which enables a favorable call with small noises in a radio communication system.
It is still another object of the present invention to provide a radio communication device which enables a favorable call with small noises in a radio communication system which includes a plurality of communication systems.
On the other hand, the inventors of the present invention have analyzed and studied a two-input-method low noise amplifier (LNA: differential low noise amplifier) in which signals which have phases thereof inverted from each other) (complementary signals) are inputted. FIG. 34A and FIG. 34B respectively show circuit parts including a low noise amplifier (LNA) 100, a high frequency voltage control oscillator (FEVCO) 101 and a mixer 102, wherein FIG. 34A indicates one-input-method LNA and FIG. 34B indicates two-input-method LNA.
In the circuit constitution which mixes an output signal from the low noise amplifier 100 which processes a reception signal from an antenna and a signal from a local oscillator (RFVCO: high frequency voltage control oscillator) 101 in a mixer 102, in the low noise amplifier having the one input constitution shown in FIG. 34A, the output frequency of the RFVCO 101 becomes equal to the output frequency of the LNA 100 and hence, when the output signal of the RFVCO 101 leaks into the LNA input line, the output signal is directly amplified at the LNA 100 and hence, there arises a drawback that an DC offset is increased.
Accordingly, as shown in FIG. 34B, by adopting the two-input method in which a differential low noise amplifier (differential amplifier: LNA) is used as the LNA 100 and signals which have phases thereof inverted from each other (complementary signals) are inputted, a DC offset is set to a small value. That is, the differential amplifier (differential amplifying circuit) 100 is comprised of two unit amplifiers having the same constitution and performs the differential amplification when two high frequency signals (complementary signals) (which have phases thereof inverted from each other) are inputted. Accordingly, the components having the same phase are cancelled and hence, it is possible to suppress the DC offset value to a small value.
However, it is found that when the carrier frequency band is further elevated, the single use of the above-mentioned two-input system which inputs the complementary signals cannot fundamentally solve the drawback on the above-mentioned DC offset. An input wiring path which allows the inputting of the above-mentioned complementary signals is roughly classified into a lead portion which is formed of a lead frame and a wire portion which connects the lead portion and electrodes of the semiconductor chip.
For example, the lead portion which is formed of a plate member made of metal such as copper has relatively large thickness and width and hence, the difference in inductance due to the minute difference in lead length of several mm is small. However, with respect to the wire portion where the diameter is approximately 20 to 30 μm, the large difference in inductance is liable to be generated due to the difference in length of the wire portion. This difference in wire inductance can be expressed as the difference in inputting time of two complementary input signals and hence, the pair characteristics of the input signals is impaired. As a result, in the high-speed communication system, the above-mentioned circuit part is not favorable with respect to a point that the gain is lowered.
Accordingly, it is another object of the present invention to enhance the pair characteristics of input signals in a circuit part which simultaneously inputs complementary signals to the differential low noise amplifier.
It is still another object of the present invention to enhance the characteristics (reduction of a DC offset) of the high frequency power module having the differential low noise amplifier.
The above-mentioned and other objects and novel features will become apparent from the description of this specification and attached drawings.